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ProGuard is a free Java class file shrinker, optimizer, and obfuscator. It removes unused classes, fields, methods, and attributes. It then optimizes the bytecode. It then renames the remaining classes, fields, and methods using short meaningless names. Finally, it preverifies the processed code for Java 6 or for Java Micro Edition.

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/*
 * ProGuard -- shrinking, optimization, obfuscation, and preverification
 *             of Java bytecode.
 *
 * Copyright (c) 2002-2007 Eric Lafortune ([email protected])
 *
 * This library is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License as published by the Free
 * Software Foundation; either version 2 of the License, or (at your option)
 * any later version.
 *
 * This library is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License
 * for more details.
 *
 * You should have received a copy of the GNU Lesser General Public License
 * along with this library; if not, write to the Free Software Foundation,
 * Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
 */
package proguard.classfile.editor;

import proguard.classfile.*;
import proguard.classfile.attribute.*;
import proguard.classfile.attribute.visitor.AttributeVisitor;
import proguard.classfile.instruction.*;
import proguard.classfile.instruction.visitor.InstructionVisitor;
import proguard.classfile.util.*;

/**
 * This AttributeVisitor computes and updates the maximum local variable frame
 * size of the code attributes that it visits.
 *
 * @author Eric Lafortune
 */
public class VariableSizeUpdater
extends      SimplifiedVisitor
implements   AttributeVisitor,
             InstructionVisitor
{
    //*
    private static final boolean DEBUG = false;
    /*/
    private static       boolean DEBUG = true;
    //*/


    // Implementations for AttributeVisitor.

    public void visitAnyAttribute(Clazz clazz, Attribute attribute) {}


    public void visitCodeAttribute(Clazz clazz, Method method, CodeAttribute codeAttribute)
    {
//        DEBUG =
//            clazz.getName().equals("abc/Def") &&
//            method.getName(clazz).equals("abc");

        // The minimum variable size is determined by the arguments.
        codeAttribute.u2maxLocals = ClassUtil.internalMethodParameterSize(method.getDescriptor(clazz));

        // Non-static methods also have the 'this' variable.
        if ((method.getAccessFlags() & ClassConstants.INTERNAL_ACC_STATIC) == 0)
        {
            codeAttribute.u2maxLocals++;
        }

        if (DEBUG)
        {
            System.out.println("VariableSizeUpdater: "+clazz.getName()+"."+method.getName(clazz)+method.getDescriptor(clazz));
            System.out.println("Max locals: "+codeAttribute.u2maxLocals+" <- parameters");
        }

        // Go over all instructions.
        codeAttribute.instructionsAccept(clazz, method, this);
    }


    // Implementations for InstructionVisitor.

    public void visitAnyInstruction(Clazz clazz, Method method, CodeAttribute codeAttribute, int offset, Instruction instruction) {}


    public void visitVariableInstruction(Clazz clazz, Method method, CodeAttribute codeAttribute, int offset, VariableInstruction variableInstruction)
    {
        int variableSize = variableInstruction.variableIndex + 1;
        if (variableInstruction.isCategory2())
        {
            variableSize++;
        }

        if (codeAttribute.u2maxLocals < variableSize)
        {
            codeAttribute.u2maxLocals = variableSize;

            if (DEBUG)
            {
                System.out.println("Max locals: "+codeAttribute.u2maxLocals+" <- "+variableInstruction.toString(offset));
            }
        }
    }
}